Lead Poisoning & Tinnitus


Lead Poisoning

Max Stanley Chartrand, Ph.D.

I recently saw a 14 year old child who was diagnosed with lead poisoning at age 3. In addition he has ADHD/LD and behavior issues. The child has reportedly noticed tinnitus for the last two to three weeks. My results include normal tympanograms, normal acoustic reflexes, normal hearing, and absent OAEs bilaterally. The physician has a ''wait and see attitude.'' Do you know of any articles that would be helpful?

Recent literature is full of publications dealing with various segments of your question, of which I can offer only a sampling. As you may already know, the correlation between learning disabilities and childhood lead poisoning has historically proven to be a strong one. What is less clear is the relationship with various otocognitive manifestations, particularly auditory neuropathy and the broader CAPDs in such cases.

But I do have a question regarding the absence of OAE amplitudes in the face of otherwise normal hearing thresholds. If hearing thresholds were within normal ranges for that age group, it would seem that utilization of either TEOAEs or DPOAEs measures would also be present.

Also, there sometimes tends to be an overestimation of what constitutes ''normal'' hearing thresholds for a child vs that of an adult. For instance, research has shown that a near-normal 16dB PTA loss during childhood can cause a number of developmental delays, including lowered reading ability. A 25dB PTA loss, even for a 14 year-old, can be considered problematic, even presenting CAPD and/or ADHD in some individuals, if the loss began during the critical period.

A good reference on the effects of milder losses is covered well in Assessment and Management of Mainstreamed Hearing-Impaired Children: Principles and Practices by Ross, Brackett and Maxon (Pro-Ed Publishing). A more compact review may also be found in my article titled ''Auditory Sensory Deprivation in Children and the Increased Role of Dispensing Professionals'' (Hearing Review, 11/96).

For other resources that may assist you in your search for answers in this case I refer you to ''Central Auditory Processing Disorders: An Overview of Assessment and Management (Schminky and Baran) @ www.tsbvi.edu/outreach/seehear/spring00/centralauditory.htm and ''Auditory Neuropathy'' (Hain) @ www.dizziness-and-balance.com/disorders/hearing/aud-neuropathy.htm.

Max Stanley Chartrand, Ph.D. is a well-known hearing health author and educator, and serves as Director of Research at DigiCare Hearing Research & Rehabilitation, Rye, CO. Correspondence: www.digicare.org.